This invention relates to an automatic soldering mechanism and an apparatus using the automatic soldering mechanism, and more particularly, to an automatic soldering mechanism for carrying out a soldering onto a both-side mounted printed-circuit board.
In general, it is known to have a both-side mounted printed-circuit board having a front surface and a back surface. Parts with leads are mounted on the front surface. Front surface mounted device is mounted on the back surface. On soldering the both-side mounted printed-circuit board, an automatic soldering mechanism is used which jets a solder jet flow from a jetting nozzle to the back surface of the both-side mounted printed-circuit board.
The soldering is carried out in a solder tank. In the solder tank, the solder jet flow is designed to have a low height. On soldering the part with a lead, the lead of the part is cut to a short length to be inserted into the both-side mounted printed-circuit board, in order to carry out the soldering.
A conventional automatic soldering mechanism is disclosed in Japanese Utility Model Publication Jikkai Sho 62-169762 (169762/1987) and will be referred to a first conventional automatic soldering mechanism. Furthermore, another conventional automatic soldering mechanism is disclosed in Japanese Patent Publication Tokkai Hei 1-266961 (266961/1989).
In the first conventional automatic soldering mechanism, a solder melt surface is raised by a solder jet flow discharged from the jetting nozzle (the jet flow port and the blowing nozzle). In the second conventional automatic soldering mechanism, the solder is flew from above the melt surface by a guide member. Therefore, it is necessary to previously cut the lead of the electronic device to a short length in order that the lead is not brought into contact with the jetting nozzle, in each of the first and the second conventional automatic soldering mechanisms. As a result, a manual working for previously cutting the lead occurs and a lot of man-hour becomes necessary.
It is theoretically possible to jet the solder jet flow discharged from the jetting nozzle above the melt surface, but it follows that the solder jet flow is oxidized on the surface thereof before reaching the both-side mounted printed-circuit board, so that it is impossible to perform a good soldering onto the both-side mounted printed-circuit board. Accordingly, it is conventionally designed so as to swell up the solder melt surface.
Oxidation of the solder surface can be prevented by extremely lowering an oxygen concentration in an inert gas atmosphere. When the oxygen concentration is made lower than 1000 ppm by the inert gas as described in Japanese Patent Publication Tokkai Hei 8-64948(64948/1996), a solder ball inevitably occurs. Since it is generally necessary to deal with the solder ball, the height of the solder jet flow is raised in the inert gas atmosphere, but it is contradictory to a common sense for those skilled in the art to make the height higher than the solder melt surface, so that conventionally it is not performed at all.
Since it is necessary to perform a soldering under a state that the lead is inserted into the both-side mounted printed-circuit board after it has been made short, stability of the electronic device becomes deteriorated, so that there is a risk of deteriorating a quality of the soldering.